1. Field of the Invention
The invention relates generally to rotary cutting tools and, more particularly, to rotary cutting tools having at least one helical flute and land having at least two margins on the land. Additionally, the invention relates to methods of producing such cutting tools.
2. Background Information
Double margin drills, such as the deep hole twist drill 50 shown in FIG. 1, are known. Such drills are of generally cylindrical shape and include a mounting portion 52 located at or near a first end 51 of drill 50 for mounting the drill 50 in a chuck mechanism (not shown) of a machine, an opposite head portion 54 located at or near an opposite second end 53 of drill 50 for engaging and cutting a workpiece (not shown), and a body relief portion 56 disposed between the mounting portion 52 and the head portion 54. Body relief portion 56 has a diameter less than the head portion 54 in order to reduce potential unnecessary contact with the edges of a hole being cut as body relief portion is not meant to perform material cutting but instead to assist in the transfer of cutting debris from head portion 54 toward mounting portion 52.
Continuing to refer to FIG. 1, deep hole twist drill 50 further includes a number of helical flutes 58, each extending from the second end 53 of the drill 50 along the head portion 54 and all, or part of, body relief portion 56. Flutes 58 provide for the discharge of cutting chips (formed from cutting operations on a workpiece) from second end 53 generally toward mounting portion 52, outward from the leading end of a hole being formed. Each flute 58 of head portion 54 is bounded by a pair of margin lands 60. Extending between the margin lands 60 of adjacent flutes 58 is margin relief surface 62 which is generally recessed inward from each of the margin lands 60. As shown in FIG. 1, such margin relief surfaces 62 extend from the second end 53 of drill 50 along all of head portion 54 and generally end at body relief portion 56. Typically, the outer diameter (not numbered) of the drill 50 in the body relief portion 56 is equal to or less than the diameter (not numbered) of the drill 50 at each of the recessed margin relief surfaces 62 such that each of the margin relief surfaces generally evenly transition into or taper down into the outer surface 64 of the body relief portion.
Such double margin drills provide for a number of advantages over other rotary cutting. However, there still exists room for improvement.